Manufacture of thin-walled containers

ABSTRACT

Metal containers, particularly for beer, have been made from stainless steel which is compatable with beer or aluminium which is specially coated to make a compatable inner surface. The stainless steel container is expensive when the wall thickness is such as to withstand rough handling and the cheaper aluminium container has a limited life depending on the internal coating. The present invention provides a double wall container of which the inner wall is of thin stainless steel. The invention solves the hitherto insurmountable problems of forming a thin walled inner vessel and expanding it inside an outer vessel so that the resulting inner vessel is without crevices which would otherwise be extremely difficult to clean to meet strict hygiene regulations.

United States ?atent 1191 Thomas 1 May 1, 1973 1 MANUFACTURE OFTHIN-WALLET) 2,198,315 4/1940 Nyberg ..113/120 L CONTAINERS 2,460,820 21949 Hagopian.... ..113 120 L 3,386,151 6/1968 Combes ..29/l57.l R [75]Inventor: Lindsay Maltland Thomas,

Chisworth, England Primary Examiner.1. Spencer Overholser AssigneezFairey Stainless i Heston, Assistant Examiner-Richard Bernard LazarusMiddlesex England AttorneyR1chard C. Sughrue et al.

[22] Filed: Dec. 2, 1971 [57] ABSTRACT [21] Appl. No.: 204,250 Metalcontainers, particularly for beer, have been made from stainless steelwhich is compatable with beer or aluminium which is specially coated tomake a [30] Forelgn Appllcanon Priority Dam compatable inner surface.The stainless steel container Dec. 2, 1970 Great Britain ..57,247/70 isexpensive when the wall thickness is such as to withstand rough handlingand the cheaper aluminium 52 us. c1. ..29/471.1, 29/480, 113/120 L,container has a limited life depending on the internal 1 3 120 Mcoating. The present invention provides a double wall 51 Int. Cl. ..B23k31/02 container of which the inner wall is of thin Stainless 581 Fieldof Search ..29/471.1, 475, 480; The invention Solves the hitherwinsurmounta- 1 133/120 L 120 M ble problems of forming a thin walledinner vessel and expanding it inside an outer vessel so that theresulting [56] References Cited inner vessel is without crevices whichwould otherwise be extremely difficult to clean to meet strict hygieneUNITED STATES PATENTS regulations- 1,788,261 1/1931 Werder ..1 13/120 M20 Claims, 8 Drawing Figures Patented May 1, 1973 3 Sheets-Sheet 1 FIG.4

lbD

' FIG.5

FIG.3

Patented May 1, 1973 3 Sheets-Sheet 2 3 Sheets-Sheet 5 28 Patented May1, 1973 FIG.7

MANUFACTURE OF THIN-WALLEI) CONTAINERS This invention relates to doublewalled containers and their manufacture. Such containers are suitablebut not exclusively for use in beer kegs.

According to one aspect of the present invention there is provided amethod of making a double wall container in which the inner vessel is athin-walled vessel of stainless steel, comprising the steps of formingtwo or more co-operating pieces of the inner vessel from sheet stainlesssteel and forming the mating edges to enable the pieces to be weldedtogether in a manner which permits subsequent flattening, straighteningor smoothing of the welded seams, welding an entry boss to one of thepieces, holding the pieces together in correct relationship and weldingthe joint or joints to form a liquid-tight container, inserting theinner vessel in a surrounding rigid outer vessel, and admitting fluidunder pressure to the interior of the inner vessel to expand it andcause it to conform substantially to the internal shape of the outervessel, thereby flattening, straightening or smoothing to a substantialdegree the welded seam or seams of the inner vessel.

According to another aspect of the invention there is provided a doublewalled container, comprising an inner thin-walled vessel of stainlesssteel and an outer rigid vessel, the inner vessel being formed from twoor more pieces of sheet stainless steel welded together in a manner suchthat after expansion of the inner vessel to conform substantially withthe inner surface of the outerivessel using fluid pressure, the weldedseam or seams are flattened, straightened or smoothed to a substantialdegree.

The hydraulic or pneumatic expansion of the inner vessel against theinner surface of the rigid outer vessel has the effect of flattening,straightening or smoothing to some degree the welded seams of the innervessel, depending upon the original form of those welded seams, andthereby of eliminating or reducing any internal crevices at these seams.

The invention thus provides a single and economical way of manufacturinga thin-walled container having a double skin, whereof the inner skin ismade of a different material from the outer skin, and whose interior issubstantially free of crevices such as would render tho-rough cleaningout of the container difficult.

The mating edges of at least one of the pieces is flanged outwards sothat, in the area of the weld the adjacent pieces are parallel to eachother or make a small included angle.

Conveniently, the inner vessel is formed of two dome shaped which areoutwardly flanged at the rims and after being brought together the twoflanges are'seam welded to give a liquid-tightjoint.

The inner vessel may be enclosed in two dome shaped portions of an outervessel and the assembly mounted in an expansion rig without the twoouter vessel portions being welded together. The interior of the innervessel is coupled to a source of hydraulic fluid and by means of thepressure of the fluid the inner vessel is expanded to conformsubstantially to the inner surface of the outer vessel, the forces onthe outer vessel being taken by the rig.

Conveniently, the entry boss is formed of a stainless steel liner havingan outwardly turned flange at the top and an inwardly turned flange atthe bottom and being internally threaded, said liner being surrounded byan aluminium sleeve which is sealingly secured thereto to provide asubstantially cylindrical assembly which passes through an aperture inthe outer vessel when the inner vessel is assembled to the outer vessel.The underside of the inwardly turned flange is provided with an annularupstand weich lies concentric and parallel with a flange formed aroundan aperture in the inner vessel to which the liner is to be welded, thewelding operation burning away a substantial part of the upstand.

If desired the inner surface of the outer vessel may be scored tofacilitate exit of air from between the inner and outer vessels duringexpansion.

The outer vessel may be provided with circumferential raised portions toact as rolling ways. The extent of the raised portions may be chosen toprovide the required degree of expansion to the inner vessel duringexpansion to flatten, straighten or smooth the welded seam.

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of the inner vessel of a double-walledcontainer, before its expansion;

FIG. 2 is an enlarged detailed sectional view of one of the weldedjoints of the inner container of FIG. 1;

FIG. 3 is a sectional view of the inner container of FIG. 1 afterexpansion;

FIGS. 4 and 5 show modified forms of welded joints which may be used inplace of that shown in FIG. 2.

FIG. is a sectional view of another embodiment of the invention, beforeexpansion of the inner container;

FIG. 7 is a similar view to that of FIG. 6, but after expansion of theinner container, and

FIG. 8 shows detail of the entry boss to the container.

In the embodiment of FIGS. 1-3, a double-walled container for use as abeer keg is manufactured as follows. Firstly an inner container 10 ismade by welding together an open-ended thin-walled sheet metal tube 1 lof stainless steel, and two thin sheet metal end plates 12 also made ofstainless steel, to form a generally cylindrical vessel as shown in FIG.ll. One of the end plates 12 has a spout portion 14 formed or welded toit. The tube 10 and the plates 12 are made of thin gauge stainless sheettypically 0.009 inch (0.2 mm) to 0.020

inch (0.5 mm) thick, for example 0.012 inch (0.3 mm). The container 10is formed by welding the edges of the end plates 12 respectively to thetop and bottom edges 15 of the tube 11, so that the plates close theopen ends of the tube.

As shown in FIG. 2, both end portions 15 of the tube 11 are bentoutwardly before welding to form circumferential flanges projectingsubstantially at right angles to the wall of the tube, the junction ofeach flange and the cylindrical wall part of the tube being smoothlycurved. The end plates 12 are placed in position against the out-turnedflanges l5, and welded joints 16 are made along these overlappedportions, close to the radially outer edges of the flanges and of theend plates, to form a closed thin-walled inner vessel of generallycylindrical flanged form.

The completed inner vessel is then placed inside a larger rigidcontainer (not shown) made for example of aluminium, or of a plasticsmaterial reinforced with aluminium, this larger container constituting arigid outer enclosure or outer wall and being also used as a mould aswill be described.

The inner container is then expanded by the admission into its interiorof pneumatic or hydraulic fluid under high pressure, to cause it toconform to the internal shape of the rigid outer container and tostraighten out and flatten the welded seams of the inner container asshown in FIG. 3. In this way the crevice which previously existedbetween each flange l5 and the margin of the adjacent end plate 12leading to the wleded joint 16 is substantially eliminated by thestraightening of the joint caused by the expansion of the inner vesselwithin the rigid outer vessel.

Another form of joint which may be used for the inner container is shownin P18. 4 and 5. In this case the margin of each end plate 12 issmoothly bent over to project at right angles to the plate 12 as acircumferenttial flange, and the outer edge of thisflange is joggledoutwardly at 20. One end of the tube 1 1 is then inserted within thejoggled portion 20 and a welded seam is made at 16D. FIG. 5 shows theshape of the joint after the inner vessel has been expanded; only a verysmall crevice remains internally at the joint.

FIGS. 6 and 7 show another embodiment of the invention for use as a beerkeg. The inner container of stainless steel comprises upper and lowerdomes 2S and 26 formed by deep pressing. in the pressing of the domes asmall flange 27 is formed at the rim of each dome. The upper dome isprovided with an aperture into which is welded an entry boss 28 as willbe described in more detail later. The upper and lower domes are broughttogether and the mating flanges 27 which make a small included angle arewelded together by plasma arc welding techniques to form acircumferential joint which stands proud of the outer surface of theinner container so formed.

As a separate operation upper and lower outer domes 29 and 30 are formedby pressing. These domes are of aluminium of approximately 2.5 mmthickness and are provided with circumferential raised portions 31 toact as rolling ways. The upper dome 29 is provided with an aperture toallow the passage of the boss 28 and the lower dome 30 is provided withan outwardly joggled edge 32 which forms a socket for the upper dome rimand a recess to accommodate the circumferential joint of the innercontainer.

The unexpanded inner container is enclosed in an upper and a lower outerdome and the assembly is inserted in an expansion rig (not shown) whichhas mould halves to accommodate the container. At this stage the outerdomes are not welded together and expansion forces are taken on the rig.The fact that the outer domes are not welded together allows escape ofthe air between the inter and outer containers when expansion occurs,allows leakages to be detected if the inner container should ruptureduring expansion, and allows limited volumetric adjustment to be made.

A hydraulic connection is made to the boss 28 and hydraulic fluid underpressure is admitted to the inner container causing it to expand toconform to the contours of the outer container. By careful metering-inof the hydraulic fluid, a close tolerance inner container capacity isobtained and established. Air from. between the containers escapesthrough the dry joint between the outer domes and if desired slightscoring may be made in the inner surface of the outer domes to faciliateair escape. During expansion the inner container enters the rolling ways31 and also the dimple 33. If desired, a small amount of adhesive may beplaced in the dimple 33 of the outer dome before assembly so that theinner container is secured to the outer to avoid the possibility ofimplosion if a vacuum should be formed during steam cleaning. Also thewelded flange formed from flanges 27 enters the recess formed betweenthe rim of the upper outer dome 28 and the joggled edge 32 of the lowerdome and in entering the recess pulls the weld to open out the creviceand straighten the joint thereby facilitating cleaning out of thecontainer.

The assembly is removed from the exapnsion rig and the joint 34 betweenthe upper and lower outer domes is formed by welding. A weld is runround the boss 28 and skirts 35 and 36 are welded to the ends of thecontainer. Skirt 35 is provided with hand holds 37 and drain holes (notshown) adjacent the container to allow spillage to drain away.

FIG. 8 shows in more detail, the construction of the boss 28, known as aBarnes neck. It is essential that an uninterrupted stainless steeelsurface is presented to the beer to be carried in the container andtherefore the boss has a stainless steel liner 38 with internalthreading. Liner 38 has an out-turned lip 39 and an inturned seating lip40 for seating a bung (not shown). Lip 40, on its surface away from itsseating surface has a downwardly directed small flange 41. Surroundingthe liner 38 is an aluminium sleeve 42 which is secured to the liner 38by an adhesive chosen to avoid any electrolytic action between the twometals. This assembly is inserted into the aperture in the upper innerdome 25, which aperture has been prepared by plunging to form aninwardly turned rim 43 which extends parallel and concentric with thesmall flange 41. The two are then welded together the metal being burneddown until the resultant weld lies substantially in the plane of theunder surface of the in-turned lip 40. The assembly now is such that itcan be inserted through the aperture in the upper outer dome 29 and indue course a weld line 44 is run around the boss.

As an alternative the sleeve 42 may be sealingly secured to the linear38 using an elastomer seal, such as an O-ring or washer, with mechanicalmeans to prevent relative rotational or axial movement. Such mechanicalmeans may include straight knurling or splining to give an interferencefit againt relative rotational movement and swaging or the like toprevent relative axial movement.

What is claimed is:

l. A method of making a double wall container comprising an inner vesselof thin walled stainless steel surrounded by a rigid outer vessel inwhich the inner vessel is a thin-walled vessel of stainless steel,comprising the steps of forming two or more co-operating pieces of theinner vessel from sheet stainless steel and forming the mating edges toenable the pieces to be welded together in a manner which permitssubsequent flattening, straightening or smoothing of the welded seams,welding an entry boss to one of the pieces, holding the pieces togetherin correct relationship and welding the pieces to form a liquid tightcontainer, inserting the inner vessel in said surrounding rigid outervessel, and admitting fluid under pressure to the interior of the innervessel to expand it and cause it to conform substantially to theinternal shape of the outer vessel, thereby flattening, straightening orsmoothing to a substantial degree the welded seam or seams of the innervessel.

2. A method as claimed in claim 1, wherein the mating edge of at leastone of the pieces is flanged outwards so that, in the area of the weldthe adjacent pieces are substantially parallel to each other, or make asmall included angle.

3. A method as claimed in claim 2, wherein the inner vessel is formed oftwo dome shaped pieces which are outwardly flaged at the rims and afterbeing brought together the two flanges are seam welded to give aliquid-tightjoint.

4. A method as claimed in claim 1, wherein the inner vessel is enclosedin two dome shaped portions of an outer vessel and the assembly ismounted in an expansion rig without the two outer vessel portions havingbeen welded to each other.

5. A method as claimed in claim 4, wherein the interior of the innervessel is coupled to a source of hydraulic fluid and by means of thepressure of the fluid the inner vessel is expanded to conformsubstantially to the inner surface of the outer vessel, the forces onthe outer vessel being taken by the rig.

6. A method as claimed in claim 5, wherein the volume of hydraulic fluidadmitted to the inner vessel is metered so that the volumetric capacityof the container is established.

7. A method as claimed in claim 6, wherein the volume of hydraulic fluidadmitted to the inner vessel is controlled so that the inner vessel isexpanded to a predetermined volumetric capacity.

8. A method as claimed in claim 1, wherein the entry boss is centrallylocated in an end face of an approximately'cylindrical container andadhesive is applied between the inner and outer vessel at least in thecentral area of the other end face.

9. A method as claimed in claim 4, wherein the two dome shaped portionsare welded together after removal from the expansion rig.

10. A method as claimed in claim 1, wherein a skirt is welded to theouter vessel to protect the entry boss from contact with the ground.

11. A method as claimed in claim 10, wherein a second skirt is welded tothe outer vessel in opposite location to the first skirt.

12. A method as claimed in claim 10, wherein the skirt is provided withhand holes to facilitate handling and/or drain holes to allow drainageof spillage.

13. A method as claimed in claim 1, wherein the entry boss is formed ofa stainless steel liner having an outwardly turned flange at the top andan inwardly turned flange at the bottom and being internally threaded,said liner being surrounded by an aluminium sleeve which is sealinglysecured thereto to provide a substantially cylindrical assembly whichpasses through an aperture in the outer vessel when the inner vessel isassemblied to the outer vessel.

14. A method as claimed in claim 13, comprising providing the undersideof the inwardly turned flange with an annular ulpstand which liesconcentric and approximately para el with a flange formed around anaperture in the inner vessel to which the liner is to be welded, andwelding the two together so that the upstand is burned substantiallyaway.

15. A method as claimed in claim 1, wherein the inner surface of theouter vessel is scored to facilitate exit of air from between the innerand outer vessels during expansion.

16. A method as claimed in claim 3, wherein the outer vessel is formedfrom two dome shaped portions of which one has ajoggled rim to form asocket for the rim of the other portion, the socket so formed alsoproviding an internal recess to accommodate the welded flanges of theinner vessel.

17. A method as claimed in claim 16, wherein the dome shaped portionsare provided with circumferential raised portions to act as rollingways.

18. A method as claimed in claim 17, wherein the extent of the raisedportions is chosen to provide the required degree of expansion to theinner vessel during expansion to flatten, straighten or smooth thewelded seam or seams.

19. A method as claimed in claim 1, wherein the outer vessel is ofaluminium or reinforced plastics material.

20. A method as claimed in claim 1, wherein the stainless steel innervessel is made from sheet stainless steel of 0.009 0.020 inches (0.2 0.5mm) thickness.

1. A method of making a double wall container comprising an inner vesselof thin walled stainless steel surrounded by a rigid outer vessel inwhich the inner vessel is a thin-walled vessel of stainless steel,comprising the steps of forming two or more cooperating pieces of theinner vessel from sheet stainless steel and forming the mating edges toenable the pieces to be welded together in a manner which permitssubsequent flattening, straightening or smoothing of the welded seams,welding an entry boss to one of the pieces, holding the pieces togetherin correct relationship and welding the pieces to form a liquid tightcontainer, inserting the inner vessel in said surrounding rigid outervessel, and admitting fluid under pressure to the interior of the innervessel to expand it and cause it to conform substantially to theinternal shape of the outer vessel, thereby flattening, straightening orsmoothing to a substantial degree the welded seam or seams of the innervessel.
 2. A method as claimed in claim 1, wherein the mating edge of atleast one of the pieces is flanged outwards so that, in the area of theweld the adjacent pieces are substantially parallel to each other, ormake a small included angle.
 3. A method as claimed in claim 2, whereinthe inner vessel is formed of two dome shaped pieces which are outwardlyflaged at the rims and after being brought together the two flanges areseam welded to give a liquid-tight joint.
 4. A method as claimed inclaim 1, wherein the inner vessel is enclosed in two dome shapedportions of an outer vessel and the assembly is mounted in an expansionrig without the two outer vessel portions having been welded to eachother.
 5. A method as claimed in claim 4, wherein the interior of theinner vessel is coupled to a source of hydraulic fluid and by means ofthe pressure of the fluid the inner vessel is expandEd to conformsubstantially to the inner surface of the outer vessel, the forces onthe outer vessel being taken by the rig.
 6. A method as claimed in claim5, wherein the volume of hydraulic fluid admitted to the inner vessel ismetered so that the volumetric capacity of the container is established.7. A method as claimed in claim 6, wherein the volume of hydraulic fluidadmitted to the inner vessel is controlled so that the inner vessel isexpanded to a predetermined volumetric capacity.
 8. A method as claimedin claim 1, wherein the entry boss is centrally located in an end faceof an approximately cylindrical container and adhesive is appliedbetween the inner and outer vessel at least in the central area of theother end face.
 9. A method as claimed in claim 4, wherein the two domeshaped portions are welded together after removal from the expansionrig.
 10. A method as claimed in claim 1, wherein a skirt is welded tothe outer vessel to protect the entry boss from contact with the ground.11. A method as claimed in claim 10, wherein a second skirt is welded tothe outer vessel in opposite location to the first skirt.
 12. A methodas claimed in claim 10, wherein the skirt is provided with hand holes tofacilitate handling and/or drain holes to allow drainage of spillage.13. A method as claimed in claim 1, wherein the entry boss is formed ofa stainless steel liner having an outwardly turned flange at the top andan inwardly turned flange at the bottom and being internally threaded,said liner being surrounded by an aluminium sleeve which is sealinglysecured thereto to provide a substantially cylindrical assembly whichpasses through an aperture in the outer vessel when the inner vessel isassemblied to the outer vessel.
 14. A method as claimed in claim 13,comprising providing the underside of the inwardly turned flange with anannular upstand which lies concentric and approximately parallel with aflange formed around an aperture in the inner vessel to which the lineris to be welded, and welding the two together so that the upstand isburned substantially away.
 15. A method as claimed in claim 1, whereinthe inner surface of the outer vessel is scored to facilitate exit ofair from between the inner and outer vessels during expansion.
 16. Amethod as claimed in claim 3, wherein the outer vessel is formed fromtwo dome shaped portions of which one has a joggled rim to form a socketfor the rim of the other portion, the socket so formed also providing aninternal recess to accommodate the welded flanges of the inner vessel.17. A method as claimed in claim 16, wherein the dome shaped portionsare provided with circumferential raised portions to act as rollingways.
 18. A method as claimed in claim 17, wherein the extent of theraised portions is chosen to provide the required degree of expansion tothe inner vessel during expansion to flatten, straighten or smooth thewelded seam or seams.
 19. A method as claimed in claim 1, wherein theouter vessel is of aluminium or reinforced plastics material.
 20. Amethod as claimed in claim 1, wherein the stainless steel inner vesselis made from sheet stainless steel of 0.009 - 0.020 inches (0.2 - 0.5mm) thickness.